The Synthesis,Characterization And Biological Applications Of Water-soluble Conjugated Polymer With Specific Cleavable Linkages

Water-soluble conjugated polymers(WSCP)had potential application prospect by the virtue of good photo-electrical property and biocompatibility which were gathered great attention of material science.While,traditional WSCP got drawbacks not only in water solubility,but also in detection property(sensitivity and selectivity).Ionic WSCP had poor specificity due to the electrostatic interaction.Although neutral WSCP immensely increased the specificity by binding targeting moieties,they got poor spectral variability.The other aspect of sensors,there was a special chemical bond called cleavable linker,which could be cleaved specifically.So such linkages could work as targeting moieties in probes.While,the majority of these probes involved in small weighted fluorophores,which were reported to have poor stability or low quantum yield.So,herein we raised a proposal that we could design a WSCP probe with specific cleavable linkages,which combined the good photo-electrical property of the conjugated polymers and specificity of the cleavable linkages.This paper is comprised of the following parts:(1)A Water-soluble Conjugated Polymer for Thiol Detection Based on “Turn-off” EffectWe investigated a novel water-soluble conjugated polymer(WSCP)for thiol detection based on ?turn-off? effect.This WSCP was modified with poly(ethylene glycol)(PEG)by disulfide linkages to achieve good solubility in aqueous solution(34 mg/m L)and high quantum yield(0.47).The separation of water-soluble PEG chains from the conjugated backbone induced by the cleavage of the disulfide linkages would lead to a significant decrease of the water solubility and a dramatical fluorescence quenching of the probe.The fluorescence intensity of the probe showed a good linear relationship with GSH(1-200 n M),and the detection limit was 16 n M.This WSCP probe was confirmed to be a good sensing material with high selectivity to thiols by testing various biological molecules.And this WSCP probe exhibited good detection effect to intracellular thiols by testing Hela cells.(2)A Water-soluble Conjugated Polymer with Pendant Disulfide Linkages to PEG Chains: A Highly Efficient Ratiometric Probe with Solubility Induced Fluorescence Conversion for Thiol DetectionIn this study,we investigated a water-soluble conjugated polymer with pendant disulfide linkages to poly(ethylene glycol)chains,which was a highly efficient ratiometric probe with solubility-induced fluorescence conversion for thiol detection.This WSCP was doped with a low-bandgap fluorophore,1,4-dithienyl benzothiadiazole(DBT),and was modified with PEGs by disulfide linkages to increase its water solubility(28 mg/m L).The separation of water-soluble PEG chains from the conjugated backbone induced by the cleavage of the disulfide linkages would lead to a significant decrease of the water solubility of the probe,which induced a significant enhancement of energy transfer efficiency.The fluorescence ratiometry(I628/I420)of the probe varied from the lowest value of 0.095 to 1.15(12-fold maximum enhancement).The detection limit was 2.56 ?g/m L(0.021 m M).The WSCP probe was confirmed to be a good sensing material with high selectivity for thiols by examining various biological molecules.We also successfully achieved the imaging of intracellular thiols in He La cell.(3)A FRET based Water-soluble Conjugated Polymer for thiols detectionIn this work,we designed and synthesized a ratiomatric water-soluble conjugated polymer probe(PF-PEG-Tritc).In this probe,disulfide was functionalized as a linkage between polyfluorene(PF)and rhodamine(Tritc)to form a FRET pair.Fluorescence form polyfluorene could be absorbed by rhodamine by fluorescence resonance energy transfer.So fluorescence of PF was inhibited.As the disulfide linkages were cleaved by thiols,Tritc were separated from polyfluorene banckbone,which induced a decrease of energy transfer efficiency brtween the FRET pair.The result would be a restoring fluorescence of PF and decrease one of Tritc.By that,a ratiometric fluorescence response was generated.By testing glutathione,the probe exhibited a good sensitivity and selectivity.The detection limit was 4.78 ?g/m L(15 n M).And this WSCP probe exhibited good detection effect to intracellular thiols by testing MCF-7 cells.(4)A Water-soluble Conjugated Polymer with Azobenzol Side Chains Based on “Turn-on” Effect for Hypoxia Cell ImagingIn this work,we designed and synthesized a water-soluble conjugated polymer with azobenzol side chains based on ?turn-on? fluorescence for hypoxia cell imaging.This polymer probe utilized the FRET between PF and AZO.This azobenzene derivative acted as fluorescence quencher,and could absorb the fluorescence from PF.So the WSCP probe exhibited no fluorescence(fluorescence ?off? state).As the AZO were cleaved by azoreductase,the fluorescence restored immediately(fluorescence ?on? state).Thus,the hypoxia was visualized by the storable fluorescence.By simulating hypoxia in vitro with azoreductase,the probe showed a potential sensitivity and selectivity to bio-hypoxia.Then,the cell imaging in various O2 concentrations(from 20% to 0.1%)and different cells(MCF-7 and Hela)further illustrated the sensitivity of the hypoxia WSCP probe.